Low back pain, e.g. chronic low back pain, is a common condition that affects about 80% of the adult population during their lifetime. Low back pain is not a specific disease with known pathophysiology, but rather a symptom with many causes. A direct cause, such as a tumor, a fracture, or an infection, has been estimated to be known only in approximately 5-10% of the patients. In the remaining 90-95% of the cases, low back pain is idiopathic, i.e. without known origin.
The structure in the back that seems mainly responsible for low back pain production is the intervertebral disc. An intervertebral disc is arranged between two adjacent vertebrae. The intervertebral disc is typically flexible and allows for motion between the adjacent vertebrae. It is formed by a ring of connective tissue that mainly comprises collagen, and a semi-liquid center comprising e.g. collagen and proteoglycans. The ring is called annulus fibrosus and the center is called nucleus pulposus.
Already at the age of 20-30 years, the intervertebral disc of a human starts to undergo ageing, a process often called disc degeneration. During the ageing process the intervertebral disc may leak or herniate and produce symptoms like low back pain and sciatica. The ageing of the intervertebral disc usually ends at the age of 60-80 years. At this stage, the intervertebral disc has been transformed to solid and dense connective tissue. When this occurs, the intervertebral disc will typically not produce symptoms anymore since it is less likely to leak or herniate. The ageing of the intervertebral disc further implies a reduction in disc height and a reduction of mobility of the spine.
It is known that disc degeneration will induce annular tears that may allow for communication between the center of the intervertebral disc and the outer surface of the annulus fibrosus. Thus, substances, such as inflammatory agents, from the center of the intervertebral disc may leak out onto the outer surface of the annulus fibrosus. Receptors, which are usually silent and arranged on the outer surface of the annulus fibrosus, may then be activated by inflammatory agents typically present in the center of the intervertebral disc during disc degeneration. This mechanism is suggested as one mechanism responsible for low back pain.
Another mechanism that has been suggested to be responsible for low back pain is that there may be newly formed blood vessels and nerves that grow from the outer surface of the annulus fibrosus into the center of the intervertebral disc through the annular tears. It is assumed that these nerves may produce pain when the intervertebral disc moves and exerts pressure on the nerves. One method to inhibit and disrupt such a progress is disclosed in US2007253930.
One common procedure for treating low back pain is by surgical stabilization of a vertebral segment comprising an intervertebral disc, which intervertebral disc presumably is producing pain. The rationale is to reduce movements of the pain-producing intervertebral disc in order to avoid the ingrowing nerves to be compressed and produce pain. This surgical treatment is, however, invasive, and not entirely satisfactory.
Another proposed procedure for treating low back pain, or rather sciatica, is by so-called chemonucleolysis, wherein an enzyme is injected into an intervertebral disc in order to dissolve the nucleus pulposus thereby reducing the pressure exerted by the nucleus pulposus of the intervertebral disc on e.g. a nerve.
Further, another proposed procedure for treating low back pain is by rejuvenation, or regeneration, of the intervertebral disc by introduction of e.g. cultivated disc cells and stem cells. However, it seems unlikely that the nutritionally deprived environment in the center of the intervertebral disc would successfully ensure survival of newly introduced cells.
For instance, regeneration promoted by a fibrosing agent has been disclosed in WO 2005/046746. WO 2005/046746 relates e.g. to a method comprising introducing into an intervertebral disc space of a patient in need thereof, a therapeutically effective amount of a fibrosing agent or a composition comprising a fibrosing agent. The fibrosing agent induces a fibrotic response at the intervertebral disc space of the patient, thereby providing the patient with a beneficial result. WO 2005/046746 also relates to an injectable composition comprising a fibrosing agent and a bulking agent.
However, there is still a need in the art to provide a safe and satisfactory procedure to more successfully treat low back pain.